A comparative study on Nile tilapia under different culture systems: Effect on the growth parameters and proposition of new growth models

Abstract

Tilapia culture presents high potential for income generation and hunger alleviation in developing countries. Suitable culture planning can help achieve such goals sustainably. This work aimed to comparatively evaluate the influence of semi-intensive and intensive cultivation systems of O. niloticus on condition factor, its derivatives and established growth models (Von Bertalanffy - VBGF, sigmoid Logistic - SLogistic, Brody and Gompertz) as well as on two proposed models (Michaelis-Menten hyperbolic growth – MMHG and hyperbolic Logistic - HLogistic). A linear estimation of VBGF parameters was also proposed. Weight-length relationships of tilapia were not significantly altered by the systems. Relative weights from the present study were higher in 9 out of 14 comparisons with tilapia from other natural environments and cultivations. Condition factor (K), Kmean, Krel and relative weight (Wrm) proved to be useful tools when assessing growth. In size-at-age analyzes (total length), VBGF and MMHG were the best models for intensive system whereas Gompertz and VBGF were selected for semi-intensive. Although length-at-age analyzes did not show significant differences between the systems and the growth indexes (ø and P) were slightly higher in cages than in ponds, the comparison between VBGF and Gompertz (best models for weight datasets) - connected to the condition factor investigation and to the importance of natural food - suggested that semi-intensive system specimens would reach commercial size earlier based on weight in the present conditions. The adoption of MMHG model when indicated suggests a wide field of research that could allow making inferences expanding the amplitude of growth studies.